As a technology to oxidize a metal film to transform the metal film into a metal oxide semiconductor film, an attempt to oxidize a metal film such as Cu, Zn, Al formed on a substrate through thermal oxidation or plasma oxidation to transform the metal film into a metal oxide semiconductor film has been conducted (for example, refer to Patent Document 1). For example, description of In as a dopant is found.
A method to obtain an amorphous oxide via decomposition oxidation (heat decomposition reaction) of an organic metal has also been known (for example, refer to Patent Document 2).
Also, synthesis of an oxide semiconductor thin film through a sol-gel method has been known (for example, refer to Non-Patent Document 1).
In these methods, thermal oxidation or plasma oxidation is used for the oxidation of a precursor. However, in the usual thermal oxidation method, since the treatment is carried out in a very high temperature range of 400° C. or more, the energy efficiency is not high, a relatively long processing time is needed, and the application of a light and flexible resin substrate becomes difficult because the temperature of the substrate increases as high as the treatment temperature.
In the case of plasma oxidation, since the treatment is carried out in an extremely reactive plasma space, there has been a problem that the electrode or the insulating layer is more degraded in the thin film transistor manufacturing process whereby the mobility and the off electric current (dark current) turns worse.
When a transistor is fabricated, at least a patterning of an electrode is needed on the substrate having thereon an electrode. Accordingly, it has been necessary to further form a semiconductor layer.
It has been also the same when a gate insulating layer is formed on a gate electrode. A prescribed solution for forming a gate insulating layer is applied on a substrate on which a gate electrode has already been formed, followed by drying at a temperature of 200° C. or less (refer to Patent Document 3). Accordingly, a high production efficiency is difficult to obtain because the electrode forming process and the insulating layer forming process is separated. Further, the drying of the insulating layer takes time because it is dried by external heating.
In Patent Document 4, an example of fabrication in a vacuum system is disclosed, where the production size is limited by the vessel size. Further, a high production efficiency is difficult to obtain because the electrode forming process and the insulating layer forming process is separated. In Patent Document 5, a production process of an insulating layer via an atmospheric pressure plasma CVD method is disclosed, where, also, a high production efficiency is difficult to obtain because the electrode forming process and the insulating layer forming process is obviously separated.
Further, a method of using other substance as a heat source for calcination such as using infrared light absorption of diamond like carbon (DLC) is disclosed, for example, in Non-Patent Document 2 or 3. This method is used for annealing of a-Si for semiconductors, and formation of poly-Si, in which a DCL layer is formed in the portion adjoining to Si by a vacuum sputtering technique, and annealing and crystallization of Si are carried out by irradiating infrared laser to the DLC layer. However, this method has problems in that the productivity and the material efficiency are not high because the DLC layer is formed under vacuum and the DLC layer which is fundamentally unnecessary must be removed.
Patent Documents 1: Japanese Patent Application Publication Open to Public Inspection (hereafter referred to as JP-A) No. 2003-179242
Patent Documents 2: JP-A No. 2005-223231
Patent Documents 3: JP-A No. 2004-304115
Patent Documents 4: US 2004/0124416 description
Patent Documents 5: JP-A No. 2000-185362
Non-Patent Document 1: Chemical-industry December 2006, pp 7-12.
Non-Patent Document 2: Proceeding of 4th meeting on thin-film forming material device seminar, IIa-1, pp 72-75
Non-Patent Document 3: Proceeding of 4th meeting of Thin-film forming material device seminar, P-8, pp 134-136